Data structure in database, database system for managing database and database managing method and system

ABSTRACT

Bookmark information having bookmark information indicative of a time corresponding to a given time series data piece for a predetermined time and state transition information indicative of a state of the time series data piece for the predetermined time is loaded, along with the time series data piece, in a database. The state transition information has one of a value indicative of an online state in which the data area is permitted to be retrieved, a value indicative of a loading state in which loading of data in the data area has not yet been completed and the data area is not permitted to be retrieved and a value indicative of a state in which data in the data area is empty. The time series data pieces for the predetermined times are loaded in a plurality of data areas of the database in sequence of times. Even during deletion or addition of data, all data retrieval requests need not be suppressed. In accordance with a data deletion request, state transition information corresponding to a data piece of interest is set to a value indicating that the data piece of interest is empty. For data retrieval, the state transition information can be read from a storage area being in online condition. Degradation of the performance of a database system caused by B tree indexing eccentrically extending in one direction owing to addition of time series data can be prevented.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a time series databaseprocessing system of especially ultra-large scale for storing datapieces serving as updating detailed information in sequence of timeseries in a database and for controlling addition/deletion/retrieval ofdata.

[0002] When data pieces are loaded on a database of large scale and aspecified data piece is retrieved from the database, index is generallyapplied. Indexing is effective when an item serving as a key duringretrieval can be specified. The indexing is a contrivance in whichspecified key items of a database are collected, a pointer is providedover the key items to take the form of a balanced tree (B tree), and thetree can be traced at a high speed up to a location corresponding to aleaf of the tree in accordance with information indicating which range akey of a specified value lies in. “An Introduction to Database Systems,3.4 Indexing” by C. J. Date, Addison-Wesley, 1986, pp.68-77 teaches acontrivance in which information corresponding to storage locations ofall data items can be obtained for all the data items. If the databaseis for about million cases or events, there occurs no problem but in adatabase of ultra-large scale for billion cases or trillion cases,however, the maintenance of index per se swells and especially, keyswhich are added in time series fashion may not be handled well.

[0003] When data pieces are added in time series fashion, the indexinggrows in a direction in which time increases, as shown in FIG. 1.Further, from the standpoint of deletion, it is known that as deletionof indices for which a constant time has expired proceeds, data piecesremain at only one side portion of the indexing tree and values of itemsare lost in spite of the existence of nodes on the other side portion,thereby placing the indexing in very inefficient condition. In such anevent, it is necessary that the indexing be reconstructed by a techniquecalled reorganization to delete wasteful areas in the indexing andpromote the efficiency. But in the time series database of ultra-largescale, this is not practical because work far exceeding the permissiblerange is required.

[0004] A utility for data loading uses a technique for writing datadirectly to a physical area of a database and therefore, with thisutility, data can be written at a high speed. However, the utility forhigh-speed data loading generally inhibits direct data write to thephysical area during data loading from conflicting area at otherretrieval or updating access. In other words, data load shallcompulsorily be executed while inhibiting access to a specified tablefor retrieval/updating or a part of a table for retrieval/updating. Thisforces retrieval of the database to be once stopped each time that timeseries data added almost every day is loaded. In a database ofultra-large scale, it takes one day or more for retrieval per se in someapplications. In that case, data loading cannot be permitted unlessretrieval is stopped, leading to fatal inconvenience. To avoid suchsituations, data can be added through usual data insertion operationwithout resort to data loading but in this case, the performance isdegraded by approximately by one order as compared to data loading ofphysical write type and besides, locking must be acquired for concealingdata during addition, largely affecting the performance of operation forretrieval of all cases or events in the database.

[0005] In order to delete a data piece in the database for which aconstant time has expired, the data piece is typically required to beretrieved and even in the presence of index, time comparable to that forinserting data piece by piece is consumed. In the absence of index, alldata pieces are retrieved for the purpose of deleting a data piece ofinterest and consequently, in the database of ultra-large scale, ittakes one day or more to operate only the deletion processing andpractically, the time series database cannot be materialized.

[0006] Thus, for the deletion of data for which a constant time hasexpired, time exceeding that for retrieval of all pieces of data isconsumed in the absence of index but conversely, in the presence ofindex, indexing is updated during deletion, leading to an operationwhich consumes much time as in the case of data insertion. Accordingly,it is practically difficult to realize daily data deletion for thedatabase which takes one day or more to retrieve all data pieces.

SUMMARY OF THE INVENTION

[0007] An object of the invention is to provide method and system whichcan eliminate conflict of the operation of time series data loading anddata deletion with the operation of data retrieval in a database systemand which can mitigate suppression imposed on retrieval by the system.

[0008] Another object of the invention is to provide a database managingsystem which can dispense with reorganization of an index tree whichloses balance owing to addition of time series data.

[0009] According to the present invention, there is provided a databasemanaging method for managing data pieces in a database, comprising thesteps of:

[0010] adding, to a given time series data piece for a predeterminedtime, book mark information having bookmark information indicative ofthe corresponding time and state transition information indicative of astate of the time series data piece for the predetermined time;

[0011] providing, as the state transition information, one of a valueindicative of an online state in which a data area is permitted to beretrieved, a value indicative of a loading state in which loading ofdata in the data area has not yet been completed and the data area isnot permitted to be retrieved, and a value indicative of an empty statein which data in the data area is empty; and

[0012] loading time series data pieces for the predetermined time in aplurality of data areas in the database in sequence of timescorresponding to the time series data pieces.

[0013] The method further comprises the steps of:

[0014] reading, from the plurality of data areas, a plurality ofbookmark information pieces each having state transition information andbookmark information in accordance with a data retrieval request appliedto the database by designating a time; and

[0015] detecting the bookmark information including the designated timeand when the state transition information included in the detectedbookmark information indicates the online state, reading a time seriesdata piece corresponding to the detected bookmark information.

[0016] When the state transition information included in the detectedbookmark information indicates either a value indicative of the loadingstate or a value indicative of the empty state, it can be decided thatthe data retrieval request is not responded to.

[0017] The method further comprises the steps of:

[0018] reading, from the plurality of data areas, a plurality ofbookmark information pieces each having state transition information andbookmark information in accordance with a data deletion request appliedto the database by designating a time; and

[0019] detecting the bookmark information including the designated timeand when the state transition information included in the detectedbookmark information indicates the online state, setting a valueindicative of the empty state in the state transition informationincluded in the detected bookmark information.

[0020] The method further comprises the steps of:

[0021] cumulating repeatedly applied time series data pieces in acumulative data storage area until they reach total data for thepredetermined time; and

[0022] after the repeatedly applied time series data pieces have beencollected up to the total data for the predetermined time, adding, to adata piece in the cumulative data storage area, bookmark informationhaving bookmark information indicative of a time corresponding to thedata piece for the predetermined time and state transition informationindicative of a state of the data piece for the predetermined time andloading resulting data pieces in the plurality of data areas in thedatabase in sequence of times corresponding to the time series datapieces.

[0023] According to the present invention, a data structure realized ina database comprises:

[0024] a plurality of data areas for loading given time series datapieces at predetermined locations of the database in sequence of times;and

[0025] a predetermined bookmark information area having bookmarkinformation indicative of a time corresponding to a time series datapiece loaded in each of the data areas and state transition informationindicative of a state of the data piece in each data area,

[0026] wherein the state transition information has one of a valueindicative of an online state in which the data area is permitted to beretrieved and a value indicative of a loading state in which loading ofdata in the data area has not yet been completed and the data area isnot permitted to be retrieved. The data pieces are arrangedconsecutively in the database while having a predetermined data capacityso that the plurality of bookmark information areas in the plurality ofdata areas may be read consecutively.

[0027] In the present invention, the database is divided into segmentswhich are each minimum blocks for storage area management and timeseries data pieces are stored in the segments. When data is loaded onthe database, a time at which the data is loaded is stored as a bookmarkat a predetermined location in a start segment from which the additionstarts with the database. Thanks to the bookmark, when retrieval of timedesignation or time interval designation is carried out, the retrievalrange can be narrowed physically by utilizing the bookmark.

[0028] When data loading is effected, the database can be brought into aloading unfinished state by locating the bookmark in other place thanthe place in which the data is being loaded. Consequently, data can beloaded directly on a physical segment without affecting other retrieval.At the time that the data loading is completed, the bookmark is writtenin the above other place and the database is recognized by suchassigning a bookmark thereto.

[0029] In the case of data deletion, when data pieces following aspecified bookmark are to be deleted collectively, the areas areeffectively emptied changing the bookmark for the unit of segment withina short time without actually accessing to the data. By managing theareas of the database in a unit of segment in wrap-around fashion, thealways pooled consecutive areas can be used from one side to load dataand replenish an area from the other side of the consecutive areas.

[0030] The present invention is effective for a computer system having adatabase and especially for a database system for retrieval in whichdata pieces reach the database system in sequence of time series anddata change other than addition or insertion and deletion of time seriesdata is not carried out.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a diagram showing indices of a tree which loses balanceowing to addition/deletion of time series data.

[0032]FIG. 2 is a diagram showing an embodiment of system constructionaccording to the present invention.

[0033]FIG. 3 is a diagram showing the construction of an embodiment of astorage apparatus of the present invention.

[0034]FIG. 4 is a diagram for explaining a bookmark information area.

[0035]FIG. 5 is a flow chart of an embodiment of the retrievalprocessing.

[0036]FIG. 6 is a diagram showing the state of the storage apparatus toexplain the flow chart of FIG. 4.

[0037]FIG. 7 is a flow chart showing an embodiment of the data loadprocessing.

[0038]FIG. 8 is a diagram showing the state of the storage apparatus inmid course to explain the flow chart of FIG. 6.

[0039]FIG. 9 is a diagram showing the final state of the storageapparatus to explain the flow chart of FIG. 6.

[0040]FIG. 10 is a flow chart of an embodiment of the deletionprocessing.

[0041]FIG. 11 is a diagram showing the state of the storage apparatus inmid course to explain the flow chart of FIG. 9.

[0042]FIG. 12 is a diagram showing the construction of the storageapparatus to explain an embodiment of a wrap-around architecture.

[0043]FIG. 13 is a diagram showing the construction of anotherembodiment of the storage apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] The present invention will now be described by way of examplewith reference to the accompanying drawings.

[0045] Referring to FIG. 2, there is illustrated an embodiment of systemconstruction according to the present invention.

[0046] As shown in FIG. 2, a database system principally comprises adatabase system apparatus 10 having a central processing unit (CPU) 11and a storage apparatus 13 for physically storing data. A databasemanagement program 12 operates on the system apparatus 10 to storeactual data from a cumulative data area 8 onto the storage apparatus 13.Provided in the storage apparatus 13 are a data area 14 and a systemdefinition information area 15 for storing definition information ofdata. The area 8 may have a data entity area 8A and an empty area 8B inorder to store time series data pieces for a predetermined time andtransfer the stored data to the storage apparatus 13.

[0047] Referring to FIG. 3, the construction of the storage apparatus isshown in greater detail to give a detailed explanation of the systemdefinition information area 15 and data area 14. In the presentembodiment, the data area 14 has consecutive areas secured on thestorage apparatus 13 so as to be divided into management blocks calledsegments 20. Data pieces generated in time series fashion are puttogether in the area 8 by means of the management program 12 until theyreach an amount for a constant time. The collected data pieces arestored in one of the management block segments of the consecutive areasof the database in the form of the storage apparatus 13, along with atime for storage which is read out of a clock 9 and stored in the samesegment or otherwise at a different location. The segment 20 includes,for example, a data storage area 21 for storing real data and a bookmarkinformation area 22 for storing management information for the datastored in the data storage area 21. In the present embodiment, thesegment 20 consists of a plurality of pages each being a unit of diskinput/output.

[0048] The system definition information 15 has information for managingthe storage location of time series data, including information forpointing a segment 20 which is the oldest in time series and informationfor pointing the start of an empty segment area.

[0049] As shown in FIG. 4 useful to explain the bookmark informationarea 22, the bookmark information area includes a time information area23 for storing information concerning a time which is specific to datastored in the segment 20 and which is delivered out of the clock 9 and astatus flag area 24 for storing status flag information indicative of ashifting or transition state (to be described below) of the segment 20.The shifting or transition state is classified into three states ormodes including “online” indicating that the data storage area isaccessible, “loading” indicating that data is now being inserted and“empty” indicating that no data is present in the data storage area. Thestatus of the segment 20 shifts from one mode or state to another.

[0050] Next, the operation of the present embodiment will be described.

[0051] In the time series database, retrieval for which time isspecified is frequently practiced. For example, the title and the dateof issue of a book published by a publisher are stored in time seriesfashion in a time series database of the publisher by using the issuedate as a key and an instance will be described hereunder in which thedatabase is retrieved for a list of titles of books issued over threemonths which range from March, 1994 to May, 1994.

[0052] The retrieval processing of the present embodiment will bedescribed with reference to FIGS. 5 and 6. FIG. 5 is a flow chartshowing an embodiment of the retrieval processing in the presentembodiment and FIG. 6 is a diagram showing the state of the storageapparatus useful to explain the flow chart of FIG. 5.

[0053] In the database system of the present embodiment, information forpointing a segment 20 which stores the oldest data in time series isfirst acquired from the system definition information 15 (step 500).Then, the database system acquires time information t (February, 1994)and status information (online) from a bookmark information area 22 ofthe pointed segment 20 (step 501). Acquisition of the system definitioninformation is carried out at a high speed because a predeterminedcapacity of data can be acquired starting with the start of a pluralityof segments arrayed at equi-capacity intervals on the database.

[0054] If the acquired status information is “empty” or “loading”, thedata to be retrieved has not been stored in the segment 20 or data isnow being inserted in the segment 20 and hence it is determined thataccess is impossible and the retrieval processing ends (step 502).

[0055] If the status information is “online”, access is permitted andthe program proceeds to the next process (step 503). The posteriorretrieval request time (May, 1994) is compared with the time information(February, 1994) stored in the bookmark information area 22 to decidewhether the intended data is stored in the database. If the result ofcomparison is “Yes”, in a test whether the stored newer data is newerthan the range of the retrieval object (March, 1994 to May, 1994), theretrieval processing ends. When “No” is issued in the decision process,the program proceeds to the next process (step 504) to decide whetherthe segment 20 now pointed is within the retrieval request time (March,1994 to May, 1994). Since the segment 20 is of February, 1994, this datastorage area 21 is excluded from the retrieval object and a segment 20for storing data which succeeds in terms of time series is pointed (step506). For example, it is assumed that a magnetic disk device is used asthe storage apparatus 13 and given that all of the segments 20 have thesame size, the succeeding segment can be pointed by moving the size ofsegment (a moving amount relative to the magnetic head) starting fromthe header of the present disk.

[0056] Next, for that succeeding segment 20, the decision process likethe above (steps 502, 503 and 504) is executed. When it is determined inthe process (step 504) that the segment 20 is one which meets theretrieval request, data is read out of the corresponding data storagearea 21 in the segment 20 (step 505). Since the header of the diskpoints the start of a segment 20 which stores the next data in terms oftime series after the data has been read out of the data storage area 21(step 506), time information is again acquired from a bookmarkinformation area 22 and thereafter, the decision is repeated in asimilar way. In this manner, the segments 20 are sequentially read.Since in the decision process (step 503) of a segment 20 the segment isdetermined to be outside the retrieval object, the retrieval processingends at that time.

[0057] Next, the data load processing will be described with referenceto FIG. 7. FIG. 7 is a flow chart showing the data load processing inthe present embodiment. In the present embodiment, an instance will bedescribed in which data pieces of from July, 1994 to August, 1994 areloaded from the system apparatus to the database, that is, data loadingis carried out. It is now assumed that data pieces to be inputted in theform of files have already been sorted in terms of time series. Thefollowing description will be given by referring to an example wheredata is added to the initial state illustrated in FIG. 6.

[0058] Firstly, empty segment information is read out of the systemdefinition information 15 (step 600). An empty segment 20 is pointed bythat information. In order to read input data, the input file isaccessed and data (July, 1994) is read (step 602). Because of thepresence of the data, “presence” is determined in the process (step 602)and the program proceeds to the process (step 603). In the process (step603), a write process is executed. Firstly, the time, information (July,1994) is written at the time information area and a flag “loading”indicating currently loading at the status flag area in the bookmarkinformation area 22, and data is written into the data storage area 21.After completion of write, a state as shown in FIG. 8 prevails.

[0059] After write of data for one segment has been terminated, thedatabase system reads the next input data from the file (step 601).Because of the presence of data for August, 1994, “presence” isdetermined in the decision process (step 602). Through the same logic asthat used for writing the data for July, 1994, time information (August,1994), a status flag “loading” and data are written at the timeinformation area 23, status flag area 24 and data storage area 21 in asegment 20 (step 603).

[0060] After completion of write, the system is about to read the nextdata from the file (step 601). But, since data has already been absentin the file, “absence” is determined in the decision process (step 602)and the program proceeds to the next process (step 604 in FIG. 7).

[0061] After write of the input data to the database has been finished,the database system starts updating the status flag in the bookmarkinformation area in order to make the segments written with the new dataaccessible (step 604).

[0062] When write of the final data is completed, the database systemreads the empty segment information 16 in the system definitioninformation 15 and points a segment 20 which has initially been writtenwith the new data. Since in that segment 20 the status flag in thebookmark area 22 is set with “loading”, this flag is shifted to“online”. This permits that segment to be retrieved. In the presentembodiment, the size of segment is defined as in the case of retrievaland therefore, a segment 20 stored with the next information in timeseries fashion can be pointed.

[0063] The shift or transition processing from “loading” to “online”ends when the status flag of the read bookmark information areaindicates “empty” and address information for that segment is set in theempty segment information 16 in the system definition information 15(step 605). A state in which the data load processing is thoroughlycompleted is shown in FIG. 9. As will be seen from the above, evenduring loading, the database system need not suppress the data retrievalrequest because by adopting the flag, it is possible to realize such asetting operation that access to the disk having a segment in which the“loading” flag is not raised can be permitted and access to the diskhaving a segment in which the flag is raised cannot be permitted.

[0064] Next, the deletion processing will be described with reference toFIG. 10. FIG. 10 is a flow chart showing an embodiment of the deletionprocessing.

[0065] In the present embodiment, the state shown in FIG. 6 isconsidered as the initial state and the segment 20 for February, 1994 isdeleted.

[0066] Firstly, start segment information 16 is read out of the systemdefinition information 15 (step 700). Time information (February, 1994)is acquired from the bookmark information area 22 of the segment 20 andit is decided whether the segment 20 is one which is an object to bedeleted (step 701).

[0067] Since the deletion object is of February, 1994, that segment 20is determined to be the deletion object. The start segment information16 in the system definition information 15 is shifted to the nextsegment 20 (for March, 1994) in time series fashion. The segment size isdetermined and therefore, a start segment address can be obtained byadding by the segment size (step 702).

[0068] Subsequently, time information (null) is set to the bookmarkinformation area 22 (step 703) and “empty” is set to the status flag(step 704). By initializing the bookmark information area 22 (steps 703and 704), the segment 20 can be shifted to an inaccessible state.

[0069] A segment 20 which is next in terms of time series is pointed(step 705) and time information (March, 1994) is acquired from thebookmark information area 22 of that segment 20. The acquired timeinformation (March, 1994) is compared with February, 1994 for thedeletion object and it is determined that the segment 20 is not thedeletion object (step 701), thus ending the deletion processing. Afterthe completion, the database assumes a state as shown in FIG. 11.

[0070] In the present deletion processing, internal data need not bedirectly accessed and only the bookmark information area is taken as theobject, thereby making it possible to perform deletion within a shorttime and during online.

[0071] The segments are used in wrap-around fashion to attain anadvantage that no reorganization is needed even when addition/deletionis repeated. Finally, the wrap-around architecture will be described.

[0072] Referring now to FIG. 12, there is illustrated an embodiment ofthe wrap-around architecture. A method of wrap-around which uses therespective segments temporally cyclically can be realized by setting a“start” flag 26 and a start address area 25 in the bookmark informationarea 22 of each segment 20. In a segment which is at the physicallylowest position, “1” is set in the “start” flag 26 and an address of astart one 20 of the segments is set in the start address area 25. Evenin the processing of retrieval/deletion/insertion, this setting can berealized easily by adding a process of jumping to the start address onthe extension of the retrieval/deletion/insertion processing because theprocessing of referring to the bookmark information area is alwaysemployed in the retrieval/deletion/insertion processing. In thisexample, a database is shown which always holds data of the latest sixmonths in a minimal segment capacity.

[0073] Data pieces over a certain constant time are frequently managedby a plurality of segments 20. FIG. 13 shows an embodiment of thepresent invention which meets this case. In the present embodiment, asystem is available in which bookmark information pieces are stored in abookmark information area 22′ in the system definition information 15 soas to undergo centralized control. This system is more practical becauseit has such a merit that the area to be written with data is not limitedby the bookmark information area and the respective segments need nothave capacities which are matched to the same value.

[0074] As described above, according to the embodiments of the presentinvention, the intended data can be accessed without resort to index byretrieving thoroughly only the specified control information storagerange without retrieving the whole of the database.

[0075] In an embodiment of the present invention, data loading can beaccomplished at a very high speed without stopping retrieval bytemporarily making addition of data to a different empty segment inadvance and at the time of completion of the data loading, assigning thedata with a bookmark in the form of a table of the database.

[0076] In an embodiment of the present invention, in connection withdeletion of data for which a constant time is exceeded, a segment to bedeleted can be specified by retrieving the bookmark and the segment is aunit of area management of the database so that the area may be emptied,with the result that deletion can be accomplished within a very shorttime (typically, approximately several seconds to several minutes).

[0077] According to the present invention, the scale of the bookmarkinformation can be small as compared to the data amount which is verylarge, thus ensuring that the maintenance processing can be realizedvery easily and the bookmark information can be retrieved within a veryshort time even in a large-scale database.

[0078] According to the present invention, in a large-scale databasewhich has a very large amount of data and in which storage and deletionof data pieces which arrive in sequence of time series, high-speedretrieval can be carried out and even during online, the data load anddeletion processing can be realized.

1. A data structure realized in a database comprising: a plurality ofdata areas in which given time series data pieces are loaded in sequenceof times; and bookmark information areas respectively provided atpredetermined locations in said plurality of data areas and each havinga pair of bookmark information indicative of a time corresponding to atime series data piece loaded in each of said data areas and statetransition information indicative of a state of the data piece in eachdata area, said state transition information being allowed to have oneof a value indicative of an online state in which the data area ispermitted to be retrieved and a value indicative of a loading state inwhich loading of data in the data area has not yet been completed andthe data area is not permitted to be retrieved.
 2. A data structureaccording to claim 1, wherein said plurality of data areas have each apredetermined data capacity and are arranged consecutively in saiddatabase in order that said plurality of bookmark information areas insaid plurality of data areas can be read consecutively.
 3. A datastructure according to claim 1, wherein the state transition informationin at least one of said plurality of data areas is allowed to have oneof a value indicative of an online state in which the data area ispermitted to be retrieved, a value indicative of a loading state inwhich loading of data in the data area has not yet been completed andthe data area is not permitted to be retrieved and a value indicative ofa state in which data in the data area is empty.
 4. A data structurerealized in a database comprising: a plurality of data areas in whichgiven time series data pieces are loaded at predetermined locations,respectively, in said database in sequence of times; and predeterminedbookmark information areas each having a pair of bookmark informationindicative of a time corresponding to a time series data piece loaded ineach of said data areas and state transition information indicative of astate of the data piece in each data area, said state transitioninformation having one of a value indicative of an online state in whichthe data area is permitted to be retrieved and a value indicative of aloading state in which loading of data in each data area has not yetbeen completed and the data area is not permitted to be retrieved.
 5. Adata structure according to claim 5, said plurality of data areas haveeach a predetermined data capacity and are arranged consecutively insaid database in order that said plurality of bookmark information areasin said plurality of data areas can be read consecutively.
 6. A datastructure according to claim 4, wherein the state transition informationin at least one of said plurality of data areas has a value indicativeof an online state in which the data area is permitted to be retrieved,a value indicative of a loading state in which loading of data in thedata area has not yet been completed and the data area is not permittedto be retrieved and a value indicative of a state in which data in atleast one data area is empty.
 7. A database managing method for managingdata in a database comprising the steps of: adding, to a predeterminedlocation in a given time series data piece for a predetermined time,bookmark information having bookmark information indicative of a timecorresponding to said time series data piece for said predetermined timeand state transition information indicative of a state of said timeseries data piece for said predetermined time; providing, as said statetransition information, one of a value indicative of an online state inwhich the data area is permitted to be retrieved, a value indicative ofa loading state in which loading of data in the data area has not yetbeen completed and the data area is not permitted to be retrieved and avalue indicative of a state in which data in the data area is empty; andloading time series data pieces for predetermined times in a pluralityof data areas in said database in sequence of times corresponding tosaid time series data pieces.
 8. A database managing method according toclaim 7 further comprising the steps of: reading, from said plurality ofdata areas, a plurality of bookmark information pieces each having statetransition information and bookmark information in accordance with adata retrieval request applied to said database by designating a time;and detecting the bookmark information including said designated timeand when the state transition information included in said detectedbookmark information indicates said online state, reading a time seriesdata piece corresponding to said detected bookmark information.
 9. Adatabase managing method according to claim 7 further comprising thestep of: when the state transition information included in said detectedbookmark information indicates either a value indicative of said loadingstate or a value indicative said empty state, determining that said dataretrieval request is not responded to.
 10. A database managing methodaccording to claim 7 further comprising the steps of: reading, from saidplurality of data areas, a plurality of bookmark information pieces eachhaving state transition information and bookmark information inaccordance with a data deletion request applied to said database bydesignating a time; and detecting the bookmark information includingsaid designated time and when the state transition information includedin said detected bookmark information indicates said online state,setting a value indicative of an empty state in said state transitioninformation included in said detected bookmark information.
 11. Adatabase managing method according to claim 7 further comprising thesteps of: cumulating repeatedly applied time series data pieces in acumulative data storage area until they reach total data for saidpredetermined time; and after said repeatedly applied time series datapieces have been collected up to said total data for said predeterminedtime, adding, to a data piece in said cumulative data storage area,bookmark information having bookmark information indicative of a timecorresponding to the data piece for said predetermined time and statetransition information indicative of a state of said time series datapiece for said predetermined time and loading resulting data pieces insaid plurality of data areas of said database in sequence of timescorresponding to said time series data pieces.
 12. A database managingmethod for managing data in a database comprising the steps of: adding,to a predetermined location in a given time series data piece for apredetermined time, bookmark information having bookmark informationindicative of a time corresponding to said time series data piece forsaid predetermined time and state transition information indicative of astate of said time series data piece for said predetermined time andstart area information having a flag indicating whether the area is thefinal one of a plurality of areas in said database and an address areafor setting an address; providing, as said state transition information,one of a value indicative of an online state in which the data area ispermitted to be retrieved and a value indicative of a loading state inwhich loading of data in the data area has not yet been completed andthe data area is not permitted to be retrieved; loading time series datapieces for predetermined times in a plurality of consecutive data areasin said database in sequence of times corresponding to said time seriesdata pieces; and raising said flag of start area information in thefinal one of said plurality of consecutive data areas and setting anaddress of first one of said plurality of consecutive data areas in saidaddress area.
 13. A database managing method according to claim 12further comprising the steps of: adding, to a predetermined location ina time series data piece for a predetermined time applied so as to beloaded in said database, bookmark information having bookmarkinformation indicative of a time corresponding to said time series datapiece for said predetermined time and state transition informationindicative of a state of said time series data piece for saidpredetermined time; reading all state transition information pieces insaid database to detect bookmark information having the oldest time andloading said time series data piece for said predetermined time appliedso as to be loaded in said database in a data area corresponding to saidoldest bookmark information; and updating said oldest bookmarkinformation to said bookmark information corresponding to said loadeddata.
 14. A database managing method for managing data in a databasecomprising the steps of: reading bookmark information having bookmarkinformation indicative of a time corresponding to a given time seriesdata piece for a predetermined time and state transition informationindicative of a state of said time series data piece for saidpredetermined time from a predetermined bookmark area and setting thestate of said time series data piece in said state transitioninformation to a value indicative of a state in which data is empty soas to write said bookmark information in said database; loading giventime series data pieces for given predetermined times in a plurality ofdata areas in said database in sequence of times corresponding to saidtime series data pieces; and after the step of loading said data pieceshas been completed, writing bookmark information having bookmarkinformation indicative of a time corresponding to a time series datapiece for said predetermined time and state transition informationindicative of an online state of said time series data piece for saidpredetermined time in said predetermined bookmark area.
 15. A databasemanaging method according to claim 14 further comprising the step ofloading time series data pieces for predetermined times in a pluralityof data areas in said database in sequence of times corresponding tosaid time series data pieces.
 16. A database managing method accordingto claim 15 further comprising the steps of: reading, from saidplurality of data areas, a plurality of bookmark information pieces eachhaving state transition information and bookmark information inaccordance with a data retrieval request applied to said database bydesignating a time; and detecting the bookmark information includingsaid designated time and when the state transition information includedin said detected bookmark information indicates said online state,reading a time series data piece corresponding to said detected bookmarkinformation.
 17. A database managing method according to claim 14further comprising the step of: when the state transition informationincluded in said detected bookmark information indicates either a valueindicative of said loading state or a value indicative of said emptystate, determining that said data retrieval request is not responded to.18. A database managing method according to claim 14 further comprisingthe steps of: reading, from said plurality of data areas, a plurality ofbookmark information pieces each having state transition information andbookmark information in accordance with a data deletion request appliedto said database by designating a time; and detecting the bookmarkinformation including said designated time and when the state transitioninformation included in said detected bookmark information indicatessaid online state, setting a value indicative of said empty state insaid state transition information included in said detected bookmarkinformation.
 19. A database managing method according to claim 14further comprising the steps of: cumulating repeatedly applied timeseries data pieces in a cumulative storage area until they reach totaldata for said predetermined time; and after said repeatedly applied timeseries data pieces have been collected up to said total data for saidpredetermined time, adding, to a data piece in said cumulative datastorage area, bookmark information having bookmark informationindicative of a time corresponding to said data piece for saidpredetermined time and state transition information indicative of astate of said time series data piece for said predetermined time andloading resulting data pieces in said plurality of data areas in saiddatabase in sequence of times corresponding to said time series datapieces.
 20. A database managing system comprising: a processor having amemory for storing given time series data pieces for predetermined timesand a clock for reading times at which said time series data pieces areapplied; and a database connected to said processor and having bookmarkinformation indicative of a time corresponding to a time series datapiece for a predetermined time, state transition information indicativeof a state of said time series data piece of said predetermined time andsaid time series data pieces for said predetermined times, said statetransition information having one of a value indicative of an onlinestate in which the data area is permitted to be retrieved, a valueindicative of a loading state in which loading of data in the data areahas not yet been completed and the data area is not permitted to beretrieved and a value indicative of a state in which data in the dataarea is empty.